This invention relates generally to equipment used in the drilling and completion of subterranean wells, and more specifically to the filling and circulating of drilling fluids in a casing string as well as pumping cement into the casing to set the casing within the wellbore.
The process of drilling subterranean wells to recover oil and gas from reservoirs, consists of boring a hole in the earth down to the petroleum accumulation and installing pipe from the reservoir to the surface. Casing is a protective pipe liner within the wellbore that is cemented in place to insure a pressure-tight connection to the oil and gas reservoir. The casing is run a single joint at a time as it is lowered into the wellbore. On occasion, the casing becomes stuck and is unable to be lowered into the wellbore. When this occurs, load or weight must be added to the casing string to force the casing into the wellbore, or drilling fluid must be circulated down the inside diameter of the casing and out of the casing into the annulus in order to free the casing from the wellbore. To accomplish this, it has traditionally been the case that special rigging be installed to add axial loan to the casing string or to facilitate circulating the drilling fluid.
When running casing, drilling fluid is added to each section as it is run into the well. This procedure is necessary to prevent the casing from collapsing due to high pressures within the wellbore. The drilling fluid acts as a lubricant which facilitates lowering the casing within the wellbore. As each joint of casing is added to the string, drilling fluid is displaced from the wellbore. The prior art discloses hose assemblies, housings coupled to the uppermost portion of the casing, and tools suspended from the drill hook for filling the casing. These prior art devices and assemblies have been labor intensive to install, required multiple such devices for multiple casing string sizes, have not adequately minimized loss of drilling fluid, and have not been multi-purpose. Further, disengagement of the prior art devices from the inside of the casing has been problematic, resulting in damage to the tool, increased downtime, loss of drilling fluid, and injury to personnel.
The normal sequence for running casing involves suspending the casing from a top drive or non-top drive (conventional rotary rig) and lowering the casing into the wellbore, filling each joint of casing with drilling fluid. The filling of each joint or stand of casing as it is run into the hole is the fill-up process. Lowering the casing into the wellbore is facilitated by alternately engaging and disengaging elevator slips and spider slips with the casing string in a stepwise fashion, facilitating the connection of an additional stand of casing to the top of the casing string as it is run into the hole.
Circulation of the fluid is sometimes necessary if resistance is encountered as the casing is lowered into the wellbore, preventing the running of the casing string into the hole. This resistance to running the casing into the hole may be due to such factors as drill cuttings, mud cake, or surface tension formed or trapped within the annulus between the well bore and the outside diameter of the casing, or caving of the wellbore among other factors. In order to circulate the drilling fluid, the top of the casing must be sealed so that the casing may be pressurized with drilling fluid. Since the casing is under pressure the integrity of the seal is critical to safe operation, and to minimize the loss of expensive drilling fluid. Once the obstruction is removed the casing may be run into the hole as before.
Once the casing reaches the bottom, circulating of the drilling fluid is again necessary to test the surface piping system, to condition the drilling fluid in the hole, and to flush out wall cake and cuttings from the hole. Circulating is continued until at least an amount of drilling fluid equal to the volume of the inside diameter of the casing has been displaced from the casing and wellbore. After the drilling fluid has been adequately circulated, the casing may be cemented in place.
On jobs which utilize a side door elevator, the casing is simply suspended from a shoulder on the elevator by the casing collar. Thus, fill-up and circulation tools with friction fit sealing elements such as packer cups, and other elastomeric friction fit devices must repeatedly be inserted and removed because of the overall length requirements of the tool. This repeated insertion will, over time, result in the wearing of the elastomeric sealing element such that it will no longer automatically seal on insertion. An adjustable extension is disclosed, which allows the fill-up and circulation tool to be retracted to prevent the elastomeric seal from being inserted into the casing during the fill-up process.
Circulation alone may be insufficient at times to free a casing string from an obstruction. The prior art discloses that the fill-up and circulation tools must be rigged down in order to install tool assemblies to attach to the rig to allow the string to be rotated and reciprocated. This process requires manual labor, inherent in which is the possibility of injury or loss of life, and results in rig downtime. The potential for injury and lost rig time is a significant monetary concern in drilling operations. To eliminate his hazard and minimize lost rig time, a method and apparatus is disclosed, which allows the fill-up and circulation tool to remain rigged up while at the same time allowing the casing to be rotated and reciprocated.
After the casing has been run to the desired depth it may be cemented within the wellbore. The purpose of cementing the casing is to seal the casing to the wellbore formation. In order to cement the casing within the wellbore, the assembly to fill and circulate drilling fluid is generally removed from the drilling rig and a cementing head apparatus installed. This process is time consuming, requires significant manpower, and subjects the rig crew to potential injury when handling and installing the additional equipment flush the mud out with water prior to the cementing step. A special cementing head or plug container is installed on the top portion of the casing being held in place by the elevator. The cementing head includes connections for the discharge line of the cement pumps, and typically includes a bottom wiper plug and a top wiper plug. Since the casing and wellbore are full of drilling fluid, it is first necessary to inject a spacer fluid to segregated the drilling fluid from the cement to follow. The cementing plugs are used to wipe the inside diameter of the casing and serves to separate the drilling fluid from the cement, as the cement is carried down the casing string. Once the calculated volume of cement required to fill the annulus has been pumped, the top plug is released from the cementing head. Drilling fluid or some other suitable fluid is then pumped in behind the top plug, thus transporting both plugs and the cement contained between the plugs to an apparatus at the bottom of the casing known as a float collar. Once the bottom plug seals the bottom of the casing, the pump pressure increases, which ruptures a diaphragm in the bottom of the plug. This allows the calculated amount of cement to flow from the inside diameter of the casing to a certain level within the annulus being cemented. The annulus is the space within the wellbore between the ID of the wellbore and the OD of the casing string. When the top plug comes in contact with the bottom plug, pump pressure increases, which indicates that the cementing process has been completed. Once the pressure is lowered inside the casing, a special float collar check valve closes, which keeps cement from flowing from the outside diameter of the casing back into the inside diameter of the casing.
The prior art discloses separate devices and assemblies for (1) filling and circulating drilling fluid, and (2) cementing operations. The prior art devices for filling and circulating drilling fluid disclose a packer tube, which requires a separate activation step once the tool is positioned within the casing. The packer tubes are known in the art to be subject to malfunction due to plugging, leaks, and the like, which lead to downtime. Since each step in the well drilling process is potentially dangerous, time consuming, labor intensive and therefore expensive, there remains a need in the art to minimize any down time. There also remains a need in the art to minimize tool change out and the installation of component pieces.
Therefore, there remains a need in the drilling of subterranean wells for a tool which can be used for drilling fluid, filling and circulating, and for cementing operations.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which can be installed quickly during drilling operations.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which seals against the inside diameter of a casing having a self-energizing feature.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which minimizes the waste of drilling fluids and allows for the controlled depressurization of the system.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which may be used for every casing size.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which submits additional axial loads to be added to the casing string when necessary.
For the foregoing reasons, there is a need for a drilling fluid filling, circulating, and cementing tool which is readily adjustable in length such that damage to the sealing element is minimized.
For the foregoing reasons, there is a need for a fill-up and circulating tool which may be sealingly coupled to a casing string to allow the string to be rotated and reciprocated into the wellbore.
The present invention is directed to a method and apparatus that satisfies the aforementioned needs. A drilling fluid filling, circulating and cementing tool having features of the present invention may be utilized on rigs with top drive drilling systems and conventional rotary type rig configurations. The tool may be quickly and easily installed in a top drive or a rotary type rig arrangement. The fill-up and circulating tool of the present invention includes a mandrel having a central axial bore extending therethrough. A top sub assembly which includes a series of threaded couplings and spacers that may be threadedly connected to the upper end of the mandrel to provide proper spacing of the tool within the rigging apparatus. The lowermost portion of the mandrel may include a plurality of apertures which allows drilling fluid to flow from the bore and through the apertures during drilling fluid circulating. A lock sleeve is disposed about the outside diameter of the mandrel, and is positioned to cover the mandrel apertures during the fill-up mode of operation. A retaining spring may be disposed on the outside diameter of the mandrel to bias the lock sleeve between the fill up and circulating positions. An inverted packer cup may be fixedly connected at one end to the outside diameter of the lock sleeve. The opposite end of the cup extends radially outward and away from the outside diameter of the lock sleeve and is adapted to automatically seal against the inside diameter of the casing string when the cup is inserted into the casing. A mud saver valve and nozzle assembly may be connected to the lower end of the mandrel. The mud saver valve is actuated to the open position by increased fluid pressure from above and regulates the flow of fluid from the tool. A nozzle may be attached to the outlet of the mud saver valve to facilitate entry of the tool into the top of the casing string. This configuration is commonly used in a top drive configuration. When the tool is used in a rotary type configuration, a bayonet adapter may be installed on the inlet of the mandrel and is adapted such that fluid may be pumped directly to the tool. The tool may also be configured in a cementing and drilling fluid fill up and circulating arrangement. The cementing and drilling fluid fill up and circulating arrangement includes a cementing head assembly connected to the top of the mandrel. This configuration allows the tool to first be used for drilling fluid fill up and circulating, and then by simply removing the mud saver valve and nozzle and installing the cement wiper plug assembly, common cementing operations may begin for cementing the casing in place. The fill-up and circulating tool of the present invention as well as other such tools, which are capable of being inserted into casing may be configured with a push plate assembly to transfer the weight of the rotary rig assembly and/or top drive to the casing string in order to force the string into the wellbore.
According to the method of the present invention, when the assembly is utilized for drilling fluid fill up within the casing string, the assembly is first installed on the top drive or rotary type unit and then positioned above the casing to be filled. In on embodiment, the assembly is then lowered until the hose extension is inside of the upper end of the casing string, without engaging the sealing cup with the inside of the casing. In this position the lowermost portion of the mandrel maybe covered by the lock sleeve. The drilling fluid pumps may then be started, which causes the drilling fluid to flow through the assembly and upon generating sufficient fluid pressure will flow through the mud saver valve and out of the nozzle into the casing.
If a side door elevator is used to raise and lower the casing, full-up and circulation tools which utilize packer cups or other elastomeric friction fit devices must repeatedly be inserted and removed because of the overall length requirements of the tool. A side door elevator is generally used when relatively short strings of casing are being run. The side door elevator does not have slips to engage with the casing string. The side door elevator in the open positions lowered axially over the upper end of the casing string such that the elevator shoulder is underneath the casing collar. The side door elevator is then closed and the top of the side door elevator shoulder is engaged against the bottom surface of the casing collar thereby suspending the casing string from the side door elevator. The problem associated with the use of this type of elevator is the reduced life of the packer cup or elastomeric friction fit sealing device due to wearing against the inside diameter of the casing string. Since the side door elevator is close coupled with the casing collar, due to the required spacing of the fill-up and circulating tool, the packer cup or elastomeric sealing device is always inserted into the casing whether in the fill-up or circulating mode as each joint of casing is added to the string, resulting in repeated frictional engagement of the sealing device with the smaller inside diameter of the casing string.
The packer, whether a cup or other elastomeric device, wearing problem also occurs when the fill-up and circulation tools is in the tandem configuration. The tandem configuration comprises the use of two different sizes of packer cups or elastomeric sealing devices on a single fill-up and circulation tool to allow different casing sizes to be run without stopping to re-tool. The normal spacing of the tool in the fill-up mode is to position the tool such that the packer is approximately one (1) foot above the top of the casing string. This is not a problem when running smaller casing since both packer cups or elastomeric devices are above the casing. However, when larger diameter casing is run, the lower (smaller diameter) packer cup or elastomeric device is inserted into the casing string such that the upper (larger diameter) packer cup or elastomeric device is approximately 1 foot above the top of the casing string.
The present invention solves the problems associated with the repeated insertion of a packer cup or elastomeric sealing device into the casing string. An adjustable extension for the fill-up and circulation tool is included, which allows the tool to be retracted to a length such that the sealing devices remain above and outside of the casing string during the fill-up step.
To begin the drilling fluid circulation mode, the assembly is lowered further into the casing string to cause the sealing element to automatically engage and seal against the inside diameter of the casing, which generally fixes the sealing device cup and sliding sleeve in place with respect to the casing. Further lowering of the assembly causes the mandrel to move axially downward resulting in the mandrel apertures being exposed from the sliding sleeve. On sufficient fluid pressure from the pumps, fluid exits from the tool into the casing through the apertures and through the nozzle. Continued flow of fluid through the tool and into the casing pressurizes the drilling fluid and on sufficient pressurization causes the fluid to circulate from the inside diameter of the casing into and out of the annulus to free or dislodge the casing from the wellbore.
On occasion circulation alone will not suffice to get past a down hole obstruction. Under these circumstances rotation of the casing string, and/or reciprocation of the casing string may be required to xe2x80x9cspudxe2x80x9d the casing into the hole. The prior art fill-up and circulation tools had to be rigged down to allow a pup piece or other similar means to be attached to the top drive rig or rotary sub to allow the string to be reciprocated and rotated past the obstruction. The rigging of the fill-up and circulating tools down and up again as well as rigging up and down with the pup piece consumes considerable man-hours and rig time. The present invention offers a solution to this problem. A torque sub in combination with the fill-up and circulation tool is provided, which allows the operator to simply make-up with the coupling on the upper end of the casing with the fill-up and circulation tool remaining connected to the top drive (or rotary sub). To make-up with the casing, the spider slips are engaged against the casing fixing it in position. The elevator slips are disengaged from the casing and the top drive unit is lowered axially over the upper end of the casing to allow the threads on the torque coupling to engage with the threads on the casing coupling. The top drive is simply actuated to rotate the fill-up and circulation tool until the torque sub is threadedly connected to the casing coupling. The operator may not pick-up on the casing string to disengage the spider slips. By placing the weight of the top drive onto the casing, the entire string can then be rotated and reciprocated. The casing can then be lowered further into the wellbore. Once the casing is lowered such that the elevator is in contact with the spider, the bails can be disconnected to allow the top sub to lower the casing even further into the wellbore. The spider slips are then engaged against the casing to fix it at the rig floor. The top drive is simply reversed to disengage the torque sub from the casing coupling, and the bails may be reconnected to the elevator, or if further reciprocation is necessary left uncoupled. Now another joint of casing can be picked up to make up the joint with the casing.
When the casing is run to the desired depth and drilling fluid filling and circulation is no longer required, the assembly may be configured for the cementing process. The drilling fluid lines are disconnected and replaced with the cement pump lines. After the drilling fluid flow is stopped, the apparatus is withdrawn from the casing to expose the mud saver valve and hose extension assembly. The mud saver valve and hose extension assembly may be simply uncoupled from the lower body of the apparatus and the cement wiper plug assembly installed. The apparatus with the cement plug assembly and cement pump lines installed is then lowered back into the casing. Once the sealing device is automatically engaged with the casing the cementing process begins. The plug release mechanism may be initiated at the appropriate times during the cementing process to release the cement wiper plugs.
The fill up and circulating tool of the present invention may include a mandrel having an axial bore formed therethrough, a sealing element disposed about the mandrel, and a pressure relief housing functionally connected with the mandrel for allowing fluid to flow from the casing into the tool when the pressure in the casing is greater then the pressure in the axial bore. The pressure relief housing may include a lateral port or aperture formed therethrough. The relief housing may further include a blocking mechanism for such as an elastomeric member or ball and seat for allowing fluid to flow into the tool from the wellbore and preventing fluid flow through the port into the wellbore.
The present invention may be utilized on top-drive and rotary type rigs. Unlike the prior art devices, this invention permits the same basic tool to be utilized for all casing diameters. The only difference is in the choice of sealing device assembly diameters. Thus, the necessity of having multiple tools on hand for multiple casing diameters is eliminated. This feature is much safer, saves rigging time as well as equipment rental costs for each casing installation. The same basic assembly may be used for cementing the casing within the wellbore, saving again on rigging time and equipment rental. In addition, the assembly may be configured for drilling fluid fill up and circulating only. The prior art does not disclose a single assembly, which may be employed to fill-up and circulate drilling fluid, pressure test casing, and fill-up and circulate cement to set the casing in place.